Improving Data Security in Cloud Computing
Using RSA Algorithm and MD5 Algorithm
Shreya Srivastav
1, Neeraj Verma
2M. Tech Scholar, Department of CSE, Om Institute of Technology and Management, Juglan, Hisar, Haryana, India1 Assistant Professor and Head of Department, Department of CSE, Om Institute of Technology and Management,
Juglan, Hisar, Haryana, India2
ABSTRACT: In today’s era cloud computing becomes the most emerging technology due to the ease of access to its
services which it provides on demand over internet on pay per use pattern. The services provided by the cloud computing includes data storage, network services, software applications, platforms etc. without physically acquiring them which saves the managing and maintenance cost. Although this is a most promising technology for any kind of services which it generally provides but still there is one major drawback in it i.e. the security of data in cloud’s environment. This is the main reason which becomes the real obstacle for people to use cloud services, as they are doubtful about the security of their data so people needs the data security in cloud paradigm. So to provide data security in cloud environment and make people more confident while using the services of cloud computing we proposed our work in which we improve the security of data in cloud computing by using RSA (Rivest, Shamir, Adleman) Algorithm and MD5 hash generation algorithm. We implement these algorithms for the security of data by using MATLAB tool.
KEYWORDS: Cloud computing, RSA, MD5, Hash generation, Encryption, Decryption, Data Security
I. INTRODUCTION
What is Cloud Computing?
Figure 1: Cloud computing
The above figure 1 describes what cloud computing is in short and brief manner. As in the figure it describes that cloud computing is next generation computing, it provides infrastructure, data and application as service. Moreover it describes that internet is equal to cloud based computing and you don’t need to know where data and applications are, and then it shows new name for grid computing is Software as a service.
DATA SECURITY ISSUES IN CLOUD COMPUTING
Cloud computing is in someway is the base of any small or large size companies, as people are using cloud for running their businesses and in cloud they are sending their data, or using the cloud for data storage purpose, so the major concern of these people is the security of their data i.e. whether their data is secure in cloud or not. So data security becomes the major obstacle in using the services of cloud computing. Some of the key features which can be taken in the context of data security are Data Integrity, Privacy and Confidentiality, Data Availability, Data Location and Relocation, Storage Backup and Recovery.
The figure 2 shows the security in Cloud Computing i.e. it is very important to maintain data security in Cloud Computing. As it describes the security threats and how important to make each and every cloud secure.
Figure 2: Data security in cloud computing
Data Integrity
Privacy and Confidentiality
This is the major issue during storing the data in cloud environment, as cloud service provide (CSP) use some mechanism to ensure the privacy and confidentiality of data i.e. the user data should be very confidential and it should not be accessed by anyone else other than the authorized user moreover it should not be accessed by the cloud personnel, so it needs to maintain the privacy and confidentiality of data by using different mechanisms.
Data Availability
Data availability is another security issue in cloud computing, as cloud service provider (CSP) stores it data i n distributed manner i.e. at different locations, so to provide uninterruptible data it needs to use some mechanism.
Data Location and Relocation
In cloud computing initially it stores data at some place but after sometime it relocates the data i.e. it lo cate and relocate the data according to the availability and requirement of storage place so in that case it needs to maintain the security of data at different locations.
Storage, backup and recovery
As we know data is stored in cloud, but what happen if cloud’s storage system get corrupted or data theft occur in its storage system, so it needs to use some mechanism to provide the backup and recovery of the lost data.
RSA Algorithm
The RSA algorithm is the most popular and proven asymmetric key cryptographic algorithm . RSA stands for Ron Rivest, Adi Shamir and Len Adleman, who first publicly described it in 1977. RSA is a block cipher, in which every message is mapped to an integer. RSA consists of Public-Key and Private-Key. Once the data is encrypted with the Public-Key, it can be decrypted with the corresponding Private-Key only.
RSA algorithm involves three steps: 1. Key Generation
2. Encryption 3. Decryption
Steps
Key generation
1. Choose two distinct prime numbers p and q. For security purposes, the integers p and q should be chosen at random and should be of similar bit length.
2. Compute N = p * q. N will be used as the module for public key and private key.
3. Select the public key (i.e. the encryption key) E such that it is not a factor of (p-1) * (q-1). 4. Select the private key (i.e. the decryption key) D such that the following equation is true:
(D*E) mod (p-1) * (q-1) = 1.
Encryption
5. For Encryption, calculate the cipher text CT from the plain text PT as follows: CT = PTE mod N.
6. Send CT as the cipher text to the receiver.
Decryption
7. For Decryption, calculate the plain text PT from the cipher text CT as follows: PT = CTD mod N [11].
MD5( Message Digest 5)
One MD5 operation
A process P is first performed on b, c and d. This process is different in all the four rounds.
The variable a is added to the output of the process P (i.e. to the register abcd).
The message sub-block M[i] is added to the output of step2(i.e. to the register abcd).
The constant t[k] is added to the output of step 3 (i.e. to the register abcd).
The output of step 4 (i.e. the contents of register abcd) is circular-left shifted by s bits.(The value of s keep changing)
The variable b is added to the output of step 5 (i.e. to the register abcd).
The output of step 6 becomes the new abcd for the next step[11].
All the above steps are shown in the following figure 3 i.e. it shows the process of one MD5 operation. As it contains the process P, variables a, b, c, d, message sub-block M[i], constant t[k] for the operation of MD5 algorithm.
Figure 3: One MD5 operation
We can mathematically express a single MD5 operation as follows: a = b + ((a + Process P (b, c, d) + M[i] + t[k]) <<< s)
where
<<< s = Circular left shift by s bits
Understanding the process P
As we can see, the most crucial aspect here is to understand the process P, as it is different in the four rounds. In simple terms process P is nothing but some Boolean operations on b, c and d as shown in the following table[11].
Above table 1 describes the process of MD5 operation of 4 round, it describes process of each round on Boolean operations using b, c and d. It contains the combination of various Boolean operations like AND, OR, NOT, XOR on the variables b, c and d for the process of all four rounds.
II. RELATED WORK
Different methods are already implemented to provide the data security in cloud computing. Some authors had tried to use Steganography technique to provide the security of data in cloud. Some other authors applied RSA algorithm for data security in cloud. In this paper we are using RSA algorithm for data security and for maintaining the integrity of key during key transmission we are using MD5 hash generation algorithm and we had also implemented the method for authenticated and authorized access to data, details of the proposed work is given in the next section.
III.PROPOSED WORK
In our proposed work we are using RSA algorithm for encrypting and decrypting data and MD5 algorithm for generating the hash value of client’s public key to maintain the integrity of client’s public key during key transmission to the cloud service provider(CSP) as data is encrypted with the help of client’s public key by cloud service provider(CSP) and then it is stored in encrypted form in cloud’s environment after that the client ask for the data from the cloud service provider (CSP) then after checking the authenticity of the client, cloud service provider(CSP) sends the data to the client after which the client decrypt the data with its own private key and get the original data. We had implemented our work by using MATLAB tool.
Now the step by step process of proposed work is as follows:-
Key generation will take place on cloud side by using RSA algorithm in which the public key of cloud service provider (CSP) will known to all.
Key generation takes place on client side by using RSA algorithm in which private key as well as public key both are known to client only and it sent its public key to those whom it want to communicate.
Client will prepare to send its public key and value of N to cloud service provider (CSP), through which cloud service provider (CSP) will encrypt client’s data.
Client will encrypt its public key and value of N by using cloud service provider (CSP) public key and value of N with the help of encryption process of RSA algorithm, after that a cipher text is generated.
Client will generate the hash value of cipher text by using MD5 algorithm and then send the cipher text and the hash value to the cloud service provider (CSP).
After that cloud service provider(CSP) will receive the client message and then generate the hash value for the cipher text by using MD5 algorithm, and then match both the hash values, if both the hash values matches then it accept the message otherwise it discards the message because it indicates the tampering of data.
After accepting the message cloud service provider (CSP) decrypt the cipher text of client’s public key and N by using its own private key and N with the help of RSA algorithm.
Now, the client (user) send its data to the cloud service provider (CSP) for storing it in its cloud environment or in cloud’s database.
When the cloud service provider (CSP) receives the message or data from the client, then cloud service provider (CSP) encrypts the client’s data by using client’s public key with help of RSA algorithm and store the client’s data in encrypted form in its (cloud’s) database.
After that Client (user) request the cloud service provider(CSP) for its data, so to verify that the request is generated from the authenticated client (user) or not, client (user) encrypts its request by using its (user’s) private key with the help of RSA algorithm encryption process and then send it to the cloud service provider (CSP).
After receiving the request from client (user) to access data , the cloud service provider (CSP) will send the data to the client in encrypted form.
Then client (user) will decrypt the data by using its private key and get the original data which it requires.
IV.EXPERIMENTAL RESULTS
The experimental result of the proposed work is shown in the following figures, as figure 4 and figure 5 shows the key generation on cloud side and client side respectively, firstly it will ask for the prime numbers (p, q) on both sides i.e. the client side and CSP side then it will generate the key on both the sides with the help of RSA algorithm using MATLAB tool.
Figure 4: Key generation on cloud side Figure 5: Key generation on client side
Figure 6 shows the encryption of client’s public key and value of N by using cloud service provider (CSP) public key and N on client side with the help of RSA algorithm this process will take place on client side. Firstly it ask for cloud’s public key and N after that it ask for client’s public key and N and then it encrypts the client’s public and value of N with the help of CSP public key and N.
After that figure 7 shows the generation of hash value of the cipher text of client’s public key and N by using MD5 hash generation algorithm to maintain the integrity of public key and N during key transmission this process again takes place on client side. In this firstly it ask for the message to which hash to be generated then it generates the hash value (message digest) for the message and then that hash value is to be sent along with the message to the cloud service provider (CSP) through which CSP can check the tampering of data takes place or not.
Figure 6: Encryption of client’s public key and N Figure 7: Generation of hash on client side using MD5
Figure 8: Verification of hash value on cloud side.
Now Figure 9 shows the encryption of client’s data done by cloud service provider (CSP) by using client’s public key and N with the help of RSA algorithm and after that the cloud service provider (CSP) stores the client’s data in encrypted form. In this firstly CSP ask for the client’s public key and value of N which it receives from client after that it ask for the message which it receives from the client then it encrypts the client message with the help of client’s public key and store the data in cloud’s database in encrypted form.
Figure 9:Encryption of message on cloud side using client’s public key.
Figure 10: Decryption of message on client side using client’s private key.
V. CONCLUSION
As we all know, data security is the most important paradigm in each and every field of web, so it is in cloud computing, hence in our proposed work we are working for the security of data and maintaining the integrity of public key during key transmission by using RSA algorithm and MD5 hash generation algorithm respectively through which we meet the objectives of privacy and confidentiality of data, integrity of data, authenticated and authorized access to the data. In the end we can say that cloud computing is still an evolving technology so it requires many modifications regarding its security issues.
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